\begin{align*}
S = 
\[ \left( \begin{array}{cccc}
          2.0 & 0.0 & 0.0 & 0.0 \\
          0.0 & 1.0 & 0.0 & 0.0 \\
          0.0 & 0.0 & 0.5 & 0.0 \\ 
          0.0 & 0.0 & 0.0 & 1.0 \end{array} 
\right)\] 
\end{align*}